Canister filters, such as those for example used as automobile oil filters, water filter, or air filters, have historically consisted of pleated filter material formed into a cylinder shape around a perforated center core and placed in an enclosed canister. The filter material used in such canister filters is primarily a treated paper-type media that is unwound from large rolls, pleated, and slit to width. The media may also be cured depending on the type of treatment used. The pleated media strips are then count cut into blocks having a specified number of pleats per block.
Once in blocks of the correct size and pleat number, the pleated blocks are formed into a hollow cylinder shape with the ends thereof secured in some manner to hold the cylinder shape. A center core may also be inserted into the hollow center of the cylinder, if desired. The pleated filter material has traditionally been held in its cylindrical configuration by one or more metal clips, or by lapping the outermost pleats or by tying a string around the cylinder to hold it in shape during the next assembly procedure. This cylindrical assembly can then be capped on one or both ends by circular ring shaped end caps. This pleated filter sub-assembly may then be inserted in a canister and secured by another circular ring shaped end cap. The center core, clips, end caps and canisters have usually been formed from metallic material that may or may not be recyclable when the filter is disposed of.
Formation of the hollow cylinder-shaped filter element from the pleated blocks of filter material has been achieved by many means, including manual, semi-automatic and automatic formation. The manual and semi-automatic methods are slow and costly, and even the automatic systems available to date have inefficiencies and other drawbacks.
In addition, the current automatic systems available are designed to produce filters having metal components. However, with the current emphasis on environmental and waste disposal concerns both in the U.S. and internationally, the trend in filter formation is toward metal-free filter assemblies. New car engines, especially foreign models, are being manufactured with permanent core substitutes within the engine at the filter mounting location, thereby eliminating the need for metal center cores in the filter assemblies. New methods for filter joining are also being pursued to eliminate the need for metal clips or metal end caps. Reusable or recyclable metal canisters are also being developed wherein a used filter assembly may be separated into the metallic canister and end caps, and the non-metallic disposable pleated filter element. Until now automated equipment capable of cost effective and efficient production of such metal-free pleated filter elements has not been available.